This invention relates to an improved method for efficiently and precisely adhering and centering particles to the tacky areas on a surface containing an array of tacky and non-tacky areas and removing particles from the non-tacky areas without removing the particles from the tacky areas. This net adhering of particles on the surface only to the tacky areas is termed net population of the surface (with the particles).
The placement of particles, such as electrically conductive solder, on contact pads is critical to the adoption of array style semiconductor packages such as ball grid arrays (BGA). Such placement is also critical in the attachment of integrated circuits (IC) to packages or printed circuit boards through "flip chip" processes. Recent attempts have been made to improve, for example, solder ball interconnects, such that more reliable and/or less costly solder connections are made in electronic applications. Despite these efforts, there are still problems associated with the handling and transfer of particles, primarily conductive particles such as solder balls to form solder bumps, on the contact pads of electronic devices. However, there is still a need for further improvements, particularly with regard to the efficiency, precision, and robustness of the population process(es). As a result, improved products and methods remain a primary objective in this art area.